Germany:Study found in 08 that subway construction was risky in Cologne

Gutachten sah schon 2008 Risiken bei Kölner U-Bahn-Bau

sueddeutsche
Several warning came in concerning the danger the construction-style
One of these warnings came on 30sep2008 from Aachens university institute for Geotechniques in construction. The scientists estimated also the danger for hydraulic groundbreak (meaning the the bottom cracks for water pressuring from below) for the tunnel-stops of Colognes subway contruction in the 84 page study.
The average calculation methods for the statics of the 30 meter high sidewalls were abolished as being too unprecise by the study for the extraordinary side-conditions.
The easy approximation methods were on the dark side Due to the layered instable construction ground and the immense waterpressure.



Currently is unclear whether the statics of the 28 meter dig at Colognes Waidmarket into which the City-archive plummeted were based on such unprecise calculation methods. THe KVB board (directorate of Colognes public transportation) didnt answer a respective question of SUEDDEUTSCHE.
The constructor KVB anticipated in its publication for construction-applicants a dig-depth (minimum-binding-depth) in the tertian layer (meaning the level BELOW the ground-tertian layer is a ground that is very old, sour and compressed meaning that water flowing between the ground concrete and the layer will not press in the layer below but may also crack in the concrete above) of 2 meters as totally sufficient.